The present invention relates to a tripod and is particularly intended for a tripod which is capable of improving the telescopic extension ratio of its legs.
Widely known examples of conventional tripods include a tripod having a structure shown in FIGS. 7 through 10.
The aforementioned conventional tripod has a leg structure comprising extensible legs, each of which may consist of three segments. The tripod has a base 2 having pairs of fitting holes 1. Two each fitting holes 1 are spaced apart and face towards each other so as to constitute a pair. A rotary shaft portion 4 at the upper end portion of each first leg member 3 is rotatably fitted in each fitting hole 1. A second leg member 6 is inserted in the first leg member 3 in such a way that the distance by which the second leg member 6 projects from the first leg member 3 can be adjusted, and a third leg member 7 is inserted in the second leg member 6 in such a way that the distance by which the third leg member 7 projects from the second leg member 6 can be adjusted.
The aforementioned two rotary shaft portions 4 of the first leg member 3 are formed of the two opposing ends of the shank of a bolt 9 inserted through a bolt insertion hole 8, which is formed at the upper end portion of the first leg member 3.
Penetration holes 10 are formed near the top of the aforementioned second leg member 6, and catching members 11 which have securing protrusions 12 are secured on the outer surface of the upper end portion of the second leg member 6, with their securing protrusions 12 respectively fitted in said penetration holes 10. In the state where the second leg member 6 projects from the first leg member 3 at the maximum extension, the catching members 11 are engaged with a receiving member 15, which is fixed in the bottom of the first leg member 3, so that the second leg member 6 is prevented from unintentionally slipping off of the first leg member 3.
An operation lever supporting member 16 is attached to the outer cylindrical surface of the lower end of the first leg member 3 so that an operation lever 17 is supported by the operation lever supporting member 16. The first leg member 3 is also provided with a brake insertion hole 18, which is formed near the bottom of the first leg member 3. A brake 20 is inserted through said brake insertion hole 18. When the brake 20 is in the state that it is inserted through the brake insertion hole 18, operation of the aforementioned operation lever 17 causes the brake 20 to be pressed against a location lower than the bottom of the catching members 11 of the second leg member 6, thereby securing the second leg member 6 to the first leg member 3.
However, as the telescopic extension ratio of the conventionally structured tripod described above is small, it presents problems in that attempting to make the tripod compact when carried results in insufficient height when in use, while trying to ensure a sufficient height when in use prevents the tripod from being made sufficiently compact when carried.
To be more specific, the rotary shaft portions 4,4 of each first leg member 3 of a tripod having the conventional structure described above are formed of the two ends of the shank of the bolt 9 inserted through the bolt insertion hole 8. Therefore, when the distance by which the second leg member 6 projects from the first leg member 3 is at its minimum extension, the top of the second leg member 6 abuts against the bolt 9. In other words, the extent of contraction when the tripod is carried is reduced by the dimension equivalent to the distance A shown in FIG. 8.
The securing protrusions 12 of the catching members 11 of each second leg member 6 are formed so as to have a relatively long protruding distance. Therefore, when the distance by which the third leg member 7 projects from the second leg member 6 is at its minimum extension, the top of the third leg member 7 abuts against the securing protrusions 12, which protrude from the inner surface of the second leg member 6. In other words, the extent of contraction when the tripod is carried is reduced by the dimension equivalent to the distance B shown in FIG. 9.
Furthermore, the conventional tripod presents a problem also when securing a second leg member 6 to the associated first leg member 3 before using the tripod; when the operation lever 17 of the first leg member 3 is operated in the state where the second leg member 6 projects from the first leg member 3 to its fullest extent, the brake 20 is pressed against a location lower than the bottom of the catching members 11 of the second leg member 6. Therefore, because of the length C of the portion where the first leg member 3 overlaps the second leg member 6 as shown in FIG. 10, an excessively long overlap has to be allowed, which may make it difficult to ensure an appropriate height when the tripod is used.
In order to solve the above problems, an object of the present invention is to provide a tripod which allows for an improved telescopic extension ratio and, therefore, can be made sufficiently compact when carried and ensure a sufficient height when in use.
A tripod according to the present invention includes a base having pairs of fitting holes, two each of which are spaced apart and situated facing each other so as to constitute a pair; first leg members, each of which has a pair of coaxially extending rotary shaft portions that are integrally formed on the outer circumferential surface of the upper end portion of the first leg member and rotatably fitted in the corresponding pair of fitting holes; and second leg members respectively inserted in said first leg members so that the distance by which each second leg member projects from the associated first leg member can be adjusted and that the top end face of each second leg member is flush with the top end face of the associated first leg member when the distance by which the second leg member projects from the first leg member is at its minimum extension. With the configuration as above, as a pair of coaxially extending rotary shaft portions are integrally formed on the outer surface of the upper end portion of each first leg member, the top end face of each second leg member is flush with the top end face of the associated first leg member when the distance by which the second leg member projects from the first leg member is at its minimum extension, the embodiment is capable of improving the telescopic extension ratio and ensures the tripod to be sufficiently compact when carried and have an appropriate height when in use.
A tripod according to another feature of the present invention includes a base; first leg members rotatably attached to said base; second leg members respectively inserted in said first leg members so that the distance by which each second leg member projects from the associated first leg member can be adjusted, each second leg member having penetration holes formed near the top of the second leg member; third leg members respectively inserted in said second leg members so that the distance by which each third leg member projects from the associated second leg member can be adjusted; receiving members respectively fixed in the bottoms of said first leg base members; and catching members disposed on the outer circumferential surface of the upper end portion of each second leg member, each catching member having an acting base portion and a securing protrusion formed on the inner surface of the acting base portion and fitted in the corresponding penetration hole, said acting base portion adapted to catch the corresponding receiving member when the second leg member is projected from the associated first leg member to the fullest extent, and said securing protrusion portion protruding from the inner surface of the acting base by a distance such that there is no possibility of the securing protrusion abutting against the top of the third leg member that is inserted in the second leg member. With the configuration as above, as the securing protrusions of the catching members of each second leg member are formed such that the protruding distance of the securing protrusions is short enough to prevent the securing protrusions from abutting against the top of the associated third leg member, there is no possibility of the securing protrusion abutting against the top of the third leg member. Therefore, the invention is capable of improving the telescopic extension ratio of the tripod and ensures the tripod to be sufficiently compact when carried and have an appropriate height when in use.
According to yet another feature of the present invention, each third leg member has cutout catching members which are fixed on the outer circumferential surface of the upper end portion of the third leg member so as to prevent unintentional displacement of the third leg member, each cutout catching member having a cutout recess which is formed in the cutout catching member so as to receive therein the securing protrusion of the corresponding catching member of the second leg member when the distance by which the third leg member projects from the second leg member is at its minimum extension. As the securing protrusions of the catching members of each second leg member are respectively inserted in the cutout recesses of the catching members of the associated third leg member when the distance by which the third leg member projects from the second leg member is at its minimum extent, there is no possibility of the securing protrusion abutting against the top of the third leg member. As a result of this feature, the telescopic extension ratio of the tripod can reliably be improved.
A tripod according to yet another feature of the present invention includes a base; first leg members rotatably attached to said base, each first leg member having a brake insertion hole formed near the bottom thereof; second leg members respectively inserted in said first leg members so that the distance by which each second leg member projects from the associated first leg member can be adjusted; receiving members respectively fixed in the bottoms of said first leg base members; catching members fixed on the outer circumferential surface of the upper end portion of each second leg member and adapted to catch the corresponding receiving member when the second leg member is projected from the associated first leg member to the fullest extent; operation lever supporting members respectively fixed on the outer circumferential faces of the lower end portions of said first leg members; operation levers respectively supported by said operation lever supporting members; and brakes respectively inserted in said brake insertion holes so that by operating the associated operation lever in the state where its second leg member projects from the first leg member to the fullest extent, each brake is pushed against a portion of the outer surface of the second leg member which is located above the bottom of the catching members of the second leg member, thereby securing the second leg member to the associated first leg member. With the configuration as above, operation of an operation lever causes the brake disposed in the first leg member associated with said operation lever to be pushed against a portion of the outer surface of the associated second leg member which is located above the bottom of the catching members of the second leg member, thereby fixing the second leg member to the associated first leg member. Because of this feature, the invention is capable of reducing the length of the portion where each first leg member overlaps the second leg member when in use and, consequently, improving the telescopic extension ratio of the tripod and ensures the tripod to be sufficiently compact when carried and have an appropriate height when in use.